A former prison guard jailed for life for murdering his childhood friend Michael McGrath has filed an appeal against his sentence and conviction.

David Benbow, 54, denied killing McGrath in the Christchurch suburb of Halswell in 2017.

In October, after an earlier hung jury, Benbow was found guilty in the High Court at Christchurch.

The Crown alleged Benbow murdered the 49-year-old after finding out he was in a relationship with his partner of 17 years, Joanna Green.

David Benbow was sentenced in the High Court for murdering Michael McGrath. Photo / Alden Williams

McGrath was supposed to visit Benbow about 9am on May 22, 2017, to help him move some railway sleepers. Benbow said he never showed up, however, the Crown said the sleepers were a “ruse” and that once McGrath arrived Benbow killed him with his .22 rifle and later disposed of his body. McGrath’s body and the firearm have never been found.

Meanwhile, the defence said McGrath never showed up and that Benbow was in no better position than anyone to say what happened to him.

Earlier this month Benbow was sentenced in the High Court at Christchurch by Justice Jonathan Eaton to life imprisonment with a minimum non-parole period of 17 years.

On Thursday, a Court of Appeal spokeswoman confirmed Benbow had filed an appeal against conviction and sentence. No hearing date has been set.

Christchurch builder Michael Craig McGrath, 49, was last seen at his home in Halswell, Christchurch, in May 2017.

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‘Calculated’ murder

At sentencing, Crown prosecutor Barnaby Hawes said the victim impact statements showed the “devastating effects” of what happened.

A key issue for sentencing was whether this case falls into category of murders especially bad that it required a minimum period of imprisonment of at least 17 years without parole. The Crown asked for a minimum period of 19 years in prison.

“The murder of Mr McGrath involved calculated and lengthy planning in the way in which he was executed.”

Crown said there was a significant aggravating factor that Benbow must know where McGrath is and what happened to him.

“Mr Benbow could still say even now what occurred.”

Benbow’s defence lawyer, Kirsten Gray, told the court it was acknowledged that McGrath was a “much-loved brother, son, and friend”.

“But on Mr Benbow’s behalf, he appears before the court to be sentenced in accordance with the jury’s verdict.

“He maintains he did not kill Mr McGrath. But in accordance with the jury’s verdict, he accepts he will be sentenced to life imprisonment.”

The issue, Gray said, was that the minimum term of imprisonment should be.

She said the court had to consider Benbow’s personal circumstances. He was 55 years old, with no prior criminal convictions.

“He was an engaged and loving father … ” she said.

Benbow was remanded in custody for more than two years, with considerable delay in trial from his arrest. None of those delays were his fault, she said.

Gray said that the minimum term of imprisonment should be around 14 years, acknowledging an uplift due to the body not being located.

Sam Sherwood is a Christchurch-based reporter who covers crime. He is a senior journalist who joined the Herald in 2022, and has worked as a journalist for 10 years.